1. Field of the Invention
The present invention is generally related to outdoor advertising structures and, more particularly, to such a rotatable structure.
2. General Background
Outdoor structures such as billboards or signs used for advertising or as information or warning signs are used in a variety of locations such as on the tops of buildings, along roadsides, and at construction sites. Such structures are constantly subjected to wind from varying directions and of greatly varying velocities. Such varying conditions have necessitated that many structures be provided with substantial reinforcement to prevent damage to the structure by high velocity winds. This results in bulky structures which are expensive to manufacture and maintain. Applicant is aware of the following outdoor structures which have attempted to address similar problems.
U.S. Pat. No. 3,321,160 issued to Turnbull entitled "Rotatable Pole Base Construction" discloses a base contruction for a pole permitting relative rotation between the pole and the pole foundation so that an arm mounted on an upper portion of the pole may be swung to a different position.
U.S. Pat. No. 3,645,057 issued to Kaplan entitled "Base For Mounting A Traffic Light Pole In Rotatable And Vertically Adjustable Relation" discloses the combination of projecting pole flanges and opposing supporting and clamping members adjustable over the anchor bolts.
U.S. Pat. No. 3,521,390 issued to Carlson entitled "Signboard Wind Load Limiting Apparatus" discloses an apparatus for protecting signboards from wind damage and allowing the use of supporting columns consisting of a signboard frame having a pivot upon which one or more signboard panels are mounted for movement on an axis located closer to one side of the panel than the other and a releasable load limiting lock connected between the panel and the framework for normally holding the panel in a fixed position and for releasing the signboard when the wind loading exceeds a pre-determined value.
U.S. Pat. No. 4,503,631 issued to Kelly entitled "Blow-Through Pivotal Sign" discloses a signboard attached to a support structure to allow the signboard to rotate along a horizontal or vertical axis and a mechanism for retaining the signboard in a fixed position until a preselected torque due to wind load is applied, as well as a wind responsive retractor for retracting the retaining mechanism to prevent damage thereto after the signboard has been deflected from the fixed position and is swinging freely.
U.S. Pat. Nos. 2,454,648 issued to Green; 4,544,125 issued to Seeley; 3,899,843 issued to Doyle, et al. and 2,048,818 issued to Neil disclose the use of springs that give way in the wind to prevent damage to the sign.
U.S. Pat. Nos. 3,638,341 issued to Holmes and 1,242,429 issued to Enochty disclose the use of wind spillways to allow the wind to pass through the sign.
Applicant's own rotatable sign carying device (Ser. No. 07/349,316, now U.S. Pat. No. 4,910,898, discloses a rotatable superstructure with panel pivotally mounted therein and responsive to wind pressure applied on their surfaces.